Color television receiver



June 6, 1961 M. M. ARMSTRONG 2,987,647

COLOR TELEVISION RECEIVER Original Filed April 4, 1956 G b/0r Sou/7d Z1/ Rear Sysfem Line 7 39 Def/ecfion I 4 4/ g5 Sync.

Sepamfor Dynamic Convergence L/NE DEE g1 F/ELO DEF.

INVENTOR. Mar/yr; M. Armsfrong BY Z: 12' E 12 Claims. Cl. 315-13 Thepresent invention relates to color television receivers and moreparticularly to a system for controlling the convergence of the electronbeams in a tri-beam cathode ray tube as used in such receiver. This is acontinuation of my copending application Serial No. 576,210, filed April4, 1956.

Most present day color television receivers utilize a cathode ray imagereproducing tube wherein a plurality of beams are generated in spacedsources at one end of the tube and are made to scan a viewing screen atthe other end of the tube to produce distinct color images thereon whichappear to the human eye as an integrated color picture. One suchtri-beam cathode ray tube employs a screen composed of a plurality ofseparate phosphor dots. The dots are arranged in triad groups with thedifferent dots in each group emitting light of a different primary colorwhen impinged by an electron beam. These phosphor dots are closelyarranged in symmetrical groups or triads, and each group is aligned witha corresponding opening of an apertured disc known as a shadow mask,which is disposed between the groups of triads and the electron beamsources. Each beam source is associated with a particular dot in eachtriad and the various dots are so arranged that if each beam passesthrough the shadow mask at the proper angle it will strike only itsassociated phosphor dot. The electron beams, each modulated with colorinformation for a particular triad, are scanned across the mask andscreen so that the individual beams strike separate dots in the varioustriads. Each triad then comprises an element of the complete colorpicture and assumes a hue and brightness according to excitation thereofby the three electron beams controlled by the received signal.

It is common to space the electron beam sources equally about the axisof the cathode ray tube, and to deflect the three beams simultaneouslyby a common line and field deflection system in order that they scan thescreen. In such a system it is necessary that the three beams beconverged at the aperture of the shadow mask so that they pass throughto impinge upon the proper phosphor dots in each triad and insure thatany monochrome picture information which may be common to all threebeams will be superimposed at the shadow mask so that the integratedmonochrome picture will not exhibit fringe areas of either of the threeprimary colors. It is necessary that such beam convergence be maintainedthroughout the entire scanning cycle of the beams. However, since theelectron beams are scanned through a rather wide angle and across ashadow mask all parts of which are not equidistant from the sources ofthe beams, the amount of convergence applied to the beams must be variedduring the scanning of the beams across the screen, that is a dynamicconvergence correction must be used. It has been found that signals ofparabolic wave form at the field deflection frequency and signals ofsimilar form at the line scanning frequency may be used to produce adynamic correction which properly converges the beams in the plane ofthe shadow mask and maintains them so converged throughout the field andline scanning operation.

Various systems for developing such control signals have been proposedin the past and many of these, even Patented June 6, 1961 ones ofcomplicated and costly construction, have not given entirely suitablewave forms and have been diflicult to adjust in a given receiver,thereby making alignment of the receivers in production a time consumingand costly process. Adjustment of dynamic convergence control systemshas also been diflicult in the past due to construction variations inthe various receiver components such as deflection yokes, cathode raytubes and the like. Furthermore, there has commonly been an undesirableinter-dependence of one convergence adjustment upon another, thusrequiring considerable hit and miss technique in the adjustment.

It is an object of this invention to provide a beam convergence systemfor a color television receiver which develops signals of improved waveform and permits more exacting control of the beams in their variousscanned positions.

Another object is to provide for a tri-beam cathode ray tube aninexpensive beam controlling system wherein various adjustments of thesystem may be common to two of the beams and independent of the otherbeam to expedite assembly and alignment of a color television receiver.

A further object of the invention is to provide a dynamic convergencecontrol system which displays improved stability and which lends itselfto assembly on a portable and detachable chassis to simplify service andadjustment of the system when the receiver is in an actual location ofuse.

A feature of the invention is the provision of a dynamic beamconvergence system including a convergence coil coupled between avariable wave forming circuit tuned to the line frequency and a furthervariable wave forming circuit tuned to the second harmonic of the linefrequency so that adjustments of each such circuit may be madeindependently of the other thus simplifying exact adjustment of thesystem. The precise control provided makes it possible to compensate forvariations in components of the system, and the like.

Another feature is the provision of a beam control system having aconvergence coil to one terminal of Which is applied convergence signalsat line and field frequency and to the other terminal of which isapplied further convergence signals at line and field frequency. Theresulting intercoupling of circuits supplying the signals of differentfrequencies is arranged so that a low impedance branch in each circuitfurnishes a return path for signals from the other circuit torespectively isolate the signal sources and allow independent adjustmentthereof.

Still another feature of the invention is the provision of such a beamcontrol system wherein circuits coupled to each terminal of theconvergence coil furnish a direct current path for a DC. stabilizingcurrent for the convergence coil and further circuits coupled to eachtermi nal of the coil provide high capacity to ground so that there isan absence of critical lead length and placement in the connectionbetween the system and its associated convergence coil.

A further feature is the provision of a convergence control system forthe beams in a tri-beam cathode ray image reproducing device wherein aconvergence coil for the blue beam in such a tube is coupled to sourcesof convergence signals energized by low impedance circuits at line andfield frequencies, and coils for the green and red beams in the tube areintercoupled to one another through a balancing device and are coupledin common to sources of convergence control signals energized by lowimpedance circuits at line and field frequencies, thus reducinginterdependence of circuit controls simplifying alignment.

Further objects, features and the attending advantages I thereof will beapparent upon consideration of the fol- 3 lowing description when takenin conjunction with the accompanying drawing in which:

FIG. 1 is a block diagram showing a television receiver utilizing thepresent invention; and a FIG. 2 is a schematic diagram of a portion ofthe circuit of FIG. 1.

In the preferred form the invention provides a beam convergence systemfor a tri-beam cathode ray tube wherein a first series tuned circuitincludes a capacitor coupled to a line sweep system of the receiver andan inductor coupled to a source of convergence signals at the fieldfrequency. A second series tuned circuit also utilizes a capacitorcoupled to the line sweep system and an inductor connected to a furthersource of convergence control signals at the field frequency. The firsttuned circuit is resonant at substantially the line frequency anddevelops sine waves, portions between the. peaks of which approximateparabolas for dynamic convergence purposes. The second. tuned circuit isresonant at substantially the second harmonic of the line frequency andprovides Waves which may be combined with the waves from the firstcircuit to more closely approximate the desired signal of parabolic waveshape. A convergence coil is coupled between the capacitor and inductorjunctions of each tuned circuit. Thus signals at line frequency areapplied to each terminal of the con: vergence coil and the amplitude andphase of these signals may be independently adjusted because ofisolation provided by the convergence coil itself, which may be of muchhigher impedance than the inductors. The inductor s of the tunedcircuits also provide coupling paths to apply parabolic signals at fieldfrequency and sawtooth (or tilt) signals at field frequency to theconvergence coil. The sources of convergence signals at field frequencyare also independently adjustable due to isolation provided. All of thesources of convergence signals are energized from low impedance circuitswhich are approximately at ground potential, to further the independenceof circuit controls.

Furthermore, the sources of signals at the field frequency and theinductors of the tuned circuits form a direct current path forapplication of direct current to the convergence coil to stabilizeconvergence with line voltage variations. In a complete system for allthree beams of the cathode ray tube, one circuit as outlined above isutilized for a single convergence coil associated with the blue beam andone additional such circuit is utilized in conjunction with separatesingle convergence coils for the red and green beams, which coils arecoupled in common through an adjustable balancing cornponent to theadditional circuit.

Referring now to the drawing, FIG. 1 shows a color television receivercoupled to an antenna 11. The receiver provides signals derived from areceived television wave for the cathoderay image reproducing device 14and these signals are applied to equally spaced electron beam sources17, 18 andv 19. Sources 17-19 are associated with blue, red, and greenprimary colors and produce electron beams 21, 22 and 23 respectively. Anapertured shadow mask 25 is disposed near the screen 27 of the imagereproducing device and the beams 21-23 are converged in the individualapertures of mask 25 during the scanning operation to impinge upongroups of phosphor dots or triads such as triad 29. The dots of eachgroup'produce the colors red, blue and green when impinged by the beam.As explained previously, the triads then become a colored element of acomplete image. It may be appreciated that the apparatus is showngreatly out of proportion for the purpose of clear er explanation.herein.

Also connected to the receiver 10 is a sound system 3-1 to which isapplied a sound, subcarrier wave; which is detected and coupled to theloudspeaker 33. The. re

ceiving. apparatus further includes a synchronizing sigor fielddeflection circuit 38 and the horizontal or line deflection circuit 39,comprise the sweep system of the receiver. Circuits 38 and 39 arecoupled to the deflection yoke 41 which is disposed on the neck of thetri-beam cathode ray tube so that signals applied to this yoke by thecircuits produce suitable vertical and horizontal scanning of beams 2123across screen 27.

' It should be apparent that as the electron beams are scanned acrossthe screen they will not always converge in an aperture of mask 25 sincethe mask and screen do not have sufficient curvature to coincide withthe arc of the convergence point as the beams are scanned. The beamsources 17-19 may be tilted somewhat so that the beams will be convergedat the center of screen 27, at least to the extent possible withinmanufacturing tolerances, but since convergence would not prevail atother than the center of the screen the beams would ordinarily notimpinge their intended phosphor dots in all the triads. Accordingly, thepoint of convergence is continually varied during each line and fieldscanning cycle by means of a dynamic convergence system 42. System 42 iscoupled to field and line deflection circuits 38 and 39 and iscontrolled by signals from these circuits. The output of the convergencesystem is applied to the dynamic convergence coils 45, 46 and 47, andthese coils are mounted. adjacent the paths of beams from sources 17, 18and 19 respectively so as. to develop fields which cause properconvergence of the beams.

FIG. 2 shows circuit connections, of a portion of the receiving systemof FIG. 1 in greater detail. Deflection yoke 41 consists of a pair offield deflection coils 51 and '52 disposed on opposite sides of theneckof tube 14 and connected together through the fixed portion ofpotentiometer 54. Similarly line deflection coils 55 and 56 aresupported along opposite sides ofthe tube neck and are connectedtogether through a variable inductor 58. Line deflection signals ofsawtooth wave form, generally at 15.75 kc., are applied to coils 55 and56 through a connection to the center tap of variable inductor 58, andat the common .conection of the coils from a winding 60 on thehorizontal or line output transformer 62 in circuit 39. Similarlydeflection signals at the field frequency, ordinarily 60v cycles persecond, are applied to the movable arm of potentiometer 54 and thecommon connection of coils 51 and 52 from winding 64 of the vertical orfield output transformer 66. Potentiometer 54 and variable inductor 58maybe mounted in a supporting device 63 on the entire deflection yoke 41as shown in FIG. 1. Adjustment of potentiometer 54 and inductor 58permits variation in the signal currents in the different yoke windingsand may be termed balancing provision of the yoke system. Adjustment ofthe balancing provision, or inductor 58, provides a variation in theline yoke field to correct for red-green horizontal line skewne ss,. ordivergenceof the horizontal traces produced'by beams from the electronguns 18, 19 of FIG. l. The balancing provision of potentiometer 54similarly allows regulationof the field deflection field to correct fordiiferences in the red-green vertical raster size, that i s, theparallel but spaced traces developed by beams from guns 18 and 19 alongthe topor bottom sides of screen 27.

By means of winding7tl of transformer 62 pulses at the line frequencyare applied acrosspotentiometer 72, resistor 73 and across potentiometer74 and resistor 75, One side of winding is connected to ground, as is.one side of winding ,77 on transformer 62'which applies pulses at linefrequency, but of opposite polarity, across potentiometers 79 andSG.

In the field deflection circuit 38, output transformer 66 includes awinding 82 which provides a signal of sawtooth wave form acrosspotentiometers 84 and 85. Center taps of potentiometer-s 84 and-85 aregrounded through resistor 87 which has a low value (e.g. 5.6 ohms) andis in 'the cathode circuit of horizontal'output tube 88.. Circut 38further. includes atransformer 90iithe primary winding 91 of which isseries coupled through the primary of output transformer 66 and to theanode of output tube 93. The other side of winding 91 is connectedthrough resistor 94 to a positive potential source. Winding 91 isshunted by an integrating capacitor 95 and the junction of resistor 94and winding 91 is by-passed to ground through capacitor 97. Resistor 94and capacitor 97 provide decoupling and filtering of the fielddeflection signal, while winding 91 and capacitor 95 provide somefurther decoupling and also integration of a portion of the field signalto render this of parabolic wave form for vertical dynamic convergencepurposes. The secondary winding 99 of transformer 93 has one terminalconnected to ground and is coupled across the fixed portions ofpotentiometers 101 and 102 to apply the parabolic wave form thereacross.

Capacitor 110 and variable inductor 111 are series coupled between avariable arm of potentiometer 72 and a variable arm of potentiometer 85.Capacitor 110 and inductor 111 comprise a series tuned circuit resonantat the line deflection frequency of 15.75 kc. This tuned circuit isenergized by pulses from winding 70 the amplitude of which may be variedby adjustment of potentiometer 72 and the phase of which may be adjustedby variation of inductor 111. The return path from inductor 111 isprovided through resistor 87 and any small portion of potentiometer 85between the mid point tap thereof and its variable arm. Similarlycapacitor 114 and variable inductor 115 are series connected between thevariable arm of potentiometer 74 and the variable arm of potentiometer'84-. Elements 114 and 115 are also series resonant at the line scanningfrequency and the return path for this circuit is also through a portionof potentiometer S4 and through resistor 87. Obviously the amplitude ofthe signal developed by this tuned circuit may be adjusted by operationof variable potentiometer 74 and the phase of the signal may beregulated by variable inductor 115.

Capacitor 121) is series connected with variable inductor 121 from thevariable arm of potentiometer 79 to the variable arm of resistor 101.Elements 120 and 121 are series resonant at the second harmonic of theline frequency and are energized by signals from winding 77 which are ofopposite phase to the signals from winding 70. The return path for thetuned circuit 120, 121 is provided through a portion of resistor 191.Similarly capacitor 124 is series connected with the variable inductor125 from the variable arm of resistor 80 to the variable arm of resistor102. Elements 124 and 125 are also series resonant at the secondharmonic of the line frequency and are energized by a signal fromWinding 77, the return path for which is provided by a portion ofresistor 102. Obviously variation of potentiometers 79 and 80 will varythe amplitudes of the signals developed by their associated circuits andadjustment of inductors 121 and 125 will vary the frequency or phase ofthe signals developed by these tuned circuits.

Dynamic convergence coil 45 which, as mentioned previously, isassociated with the blue beam produced by electron source 17, is seriesconnected between the junction of elements 110 and 111 and the junctionof elements 120 and 121. Convergence coils 46 and 4-7, which areassociated with the red and green electron beams, are essentiallyparallel coupled and have two of their terminals intercoupled throughvariable inductor 130 and the remaining terminals coupled throughpotentiometer 132. A center point of inductor 130 is connected to thejunction of capacitor 114- and inductor 115 while the arm ofpotentiometer 132 is connected to the junction of capacitor 124 adinductor 125.

Having thus described the circuit connections of the system, adescription of the operation thereof will now be given. Tuned circuit110, 111 applies a sine wave to one end of convergence coil 45, theamplitude and phase of which is adjustable by elements 72 and 111. Asunderstood in the prior art a portion of a sine wave between two peaksthereof approximates a parabola and may be used in effecting dynamicconvergence of an electron beam in a tri-beam cathode ray tube.Reference may be made to copending application of Edward J. Hague, filedNovember 30, 1954, and having Serial No. 472,033, for a description ofapparatus using wave forms which are approximately sinusoidal for thepurpose of dynamic convergence. At the other terminal of convergencecoil 45 there is applied, from resonant circuit 120 and 121, a signal atthe second harmonic of the line frequency. As has been explained in thecopending application of Kurt Schlesinger, filed September 30, 1953, andhaving Serial No. 379,998, combination of the second harmonic with thefundamental sine wave can be made to produce a resultant wave form whichclosely approximates that of the desired parabola. Through adjustment ofpotentiometer 79 and inductor 121 the resultant signal developed in coil45 is to a measurable degree the optimum wave form.

Signals of parabolic wave form at the field deflection frequency willalso be applied to one terminal of convergence coil 45 through thevariable arm of potentiometer 101 and through variable inductor 121.Furthermore, signals of sawtooth wave form at the field frequency areapplied to the other terminal of coil 45 from the vari able arm ofpotentiometer and through inductor 111. These sawtooth signals are usedfor tilt of the parabolic signals and serve to create desirabledistortion thereof for optimum convergence in a given situation. It maybe seen that coils 111 and 121 will be of comparatively low impedance atthe field frequency so that these coils have minimal effect on the fieldor vertical convergence signals. It should also be pointed out thatamplitude of the parabolic signal may be varied by adjustment ofpotentiometer 101 and that the polarity and the amplitude of the tiltsignal may be adjusted by operation of variable resistor 85 on eitherside of its center tap which is essentially grounded at the fieldfrequency by resistor 87. Intercoupling of the field convergence signalsinto the line sweep system is negligible since capacitors and bothprovide relatively high impedance for signals at the field frequency. Onthe other hand, convergence signals at line frequency do no appreciablyeffect the field deflection system since there is a comparatively lowimpedance path for these signals between the arm of potentiometer 85 andground and since the network of winding 99 and potentiometer 101 hascomparatively low impedance to ground. The step down action oftransformer 90 permits use of a relatively low integrating capacitancewith a low voltage rating across the primary winding 91, while at thesame time reducing the vertical parabolic signal source to one which isgrounded and at the required low impedance for optimum performance. Thislatter is a definite advantage. In may pervious circuits the integrationwas sensitive to, and dependent upon, the resistive load impedance ofthe combination of vertical amplitude controls and vertical convergencecoils, i.e., those placed around the tube neck. Consequently, in manycases the component variations resulted in different amplitude controlsettings and therefore, dilferent resistive load impedances which werenot optimum. Thus, the correct wave form was not realizablesimultaneously with correct amplitude settings. The use of a transformergives great latitude for impedance matching, and thus elimination of theinterdependence of the circuit controls.

While the convergence signal sources for the blue beam convergence coil45 are constructed as a separate unit, it has been found possible toprovide combined convergence signal sources for the red and greenconvergence coils 46 and 47. Accordingly, convergence signals at linefrequency are applied to coils 46 and 47 from tuned circuit 114 and 115through an adjustable balancing inductor which permits adjustment of therelative amplitudes of signals applied to the different convergencecoils. It should also be pointed out that inductor 130 may beunnecessary in many cases and merely a direct connection of the coilsmay suflice. Similarly a signal at the second harmonic of the linefrequency is applied to the other terminal of the coils 46 and 47 fromthe tuned circuit 124 and 125 and through portions of potentiometer 132,which is of low impedance at line frequency compared to that of thecoils and is insignificant. It should also be apparent that a parabolicsignal at the field frequency is applied from the arm of potentiometer1oz through inductor 125 to the coils 46 and 47 and that adjustment ofpotentiometer 132 would permit variation in the amounts of signals soapplied since the impedance of potentiometer 132 is significant comparedto that of coils 46 and 47 at field frequency. Furthermore, a tiltsignal at the field frequency is applied from the arm of potentiometer84 to the mid point of variable inductor 13%), which has a low impedanceat the field frequency, thus effectively directly applying thecorrection signals to the other terminals of coils 46 and 47. The exactoperation of the circuit associated with coils 46 and 47 and thefunction of the various components associated therewith is believedobvious after considering the operation of the system supplying signalsto coil 45. The essential difference in adjustment of the system for thered and green convergence coils is in the balancing of the lineconvergence signals between the coils by means of inductor 130 (if it isused) and in balancing of the convergence signals at field frequency bymeans of the variable potentiometer 132.

The dynamic convergence system just described is utilized to produceconvergence of the electron beams at all portions of the screen.However, in order to insure that convergence is obtained at the centerof the screen it is common to provide static convergence by means ofadjustable permanent magnets 45a, 46a, and 47a respectively associatedwith the convergence coils. Thus in the alignment of the colortelevision receiver it is usual to first adjust these permanent magnetswith the dynamic convergence system inoperative to establishconvergence'at the screen center. After this static convergence has beeneffected, the dynamic convergence system may be adjusted as previouslydescribed to obtain convergence when the beams are deflected to impingeother locations of the screen.

It should be appreciated that the effect of the dynamic convergencesystem may be changed while the effect of the static system remainsunchanged since the dynamic system relies on the use of electro-magnetsand variation of the line Voltage supplying power to the entirereceiving system may influence these, while the static system relies onthe use of steady permanent magnets. Furthermore, if the static systemis adjusted when the dynamic system is not operating, the amount ofstatic convergence necessary may be changed when the dynamic system islater energized. This can be understood by considering that signals ofparabolic wave form are applied to the convergence coil and that thesesignals will have a direct current component. This direct currentcomponent will of course influence the setting of the permanet magnetsvergence necessitated by addition of the dynamic convergence system.

The'connection of the center taps of potentiometers.

84, to cathode resistor 87 provides a DC. current flow through theconvergence coils in orderto furnish direct current for each convergencecoil which is of a D.C.' component of the dynamic signals applied to theconvergencecoils when line voltage varies. It may be seen that onecurrent path, that for blue coil, is through a a portion ofpotentiometer -85, inductor 1 11, coil 45, inductor 121 and a portionof' potentiometer 161. In

.proper amount to offset the change in the average or ductor 115,portions of inductor 130, coils 46 and 47, portions of potentiometer132, inductor 125 and a portion of potentiometer 102. Since this directcurrent for tube 38 is also supplied by the usual power supply of theentire receiving system, the amount thereof will vary with line voltagevariation and will thus follow changes in the dynamic convergence causedby line voltage variation. It has been found that a very low value ofresistance for resistor 87 will provide proper results without seriouslyaffecting horizontal size and that it is unnecessary to bypass thisresistor.

The beam convergence system further lends itself to construction on aseparate and removable chassis within the housing of the entiretelevision receiver. It may be noted that the system can be fed byseveral leads from the line and field... deflection systems andthat sixleads from the convergence system 42 run to the convergence coils 45-47.Accordingly, in a practical situation one who is undertaking to adjustthe convergence system may remove a portable chassis on which system 42is mounted, insert extensions in the leads (or alternatively the leadscould be originally made of the required length), and the chassis may bepositioned in front of the receiver where the effect of each adjustmentmade can be easily observed. It should be noted that the placement andlength of leads between the convergence coils and the source ofconvergence signals will not be critical in the circuit as described.This may be appreciated by considering the fact that each of the leadscoupling the convergence system to the convergence coils includesaseries capacitor (capacitors 110, 114, 120, 124) which is connected toground through a relatively small resistance at the frequencyencountered. Therefore, further alteration of shunt capacity introducedby changing positions of the leads will not cause an appreciable changein the total capacity existing between the leads and ground. Thus theentire system is highly practical for servicing in the field.

There is also a very desirable independence of the various controls ofthis system thus further making it easy to adjust. With the lineconvergence signal applied to one end of the convergence coil and theline second harmonic signal, or modifying signal, applied to the otherend of convergence coil, the sources are isolated from one another andadjustment of one has but minimal effect on the other. by making theimpedance of the blue convergence coil, or that of the set of red andgreen coils, ten or more times that of the inductors in the tunedcircuits. Furthermore, desirable independenceprevails in the case of-thefield deflection signals wherein the parabolic signal is applied to oneend of the convergence coil and the tilt, or correction signal, isapplied to the other end thereof. Accordingly, with the interactionamong the various controls reduced, and the use of a common signalsource for the red and green coils, 46 and 47, alignment is greatlysimplified and it is unnecessary to go through extensive cut and tryprocedures as have been required 'with some'convergence systems of thepast.

This system which provides the desired convergence wave form includes notubes and is extremely simple and inexpensive to'align because thenecessary indetire system may also be constructed on'a chassis which canbe conveniently positioned while the adjustments 1 are made. Thus it maybe appreciated that the convergence system can be regulated preciselythrough its various control provisions so' as to provide optimumconvergence despite somewhat liberal manufacturing tolerances in cathoderay tube and yoke combinations.

I claim: V '1. In a television receiver "including a cathode ray imagereproducing tube having'means for developing a plurality of cathode raybeams and scanning means in- V This isolation is increased cluding aline sweep system for deflecting the beams at a selected line frequencyand a field sweep system for deflecting the beams at a selected fieldfrequency, a control circuit for dynamically controlling the convergenceof the cathode ray beams including in combination, convergence electrodemeans adapted to be disposed adjacent the cathode ray tube to develop afield for converging a beam, a first circuit connected to the line andfield sweep systems and including first means providing convergencecontrol signals at the field frequency and means for developingconvergence control signals at the line frequency, a second circuitconnected to the line and field sweep systems and including second meansproviding further convergence control signals at the field frequency andmeans for developing convergence control signals at substantially thesecond harmonic of the line frequency, and means coupling saidconvergence electrode means to said first and sec ond circuits to applyconvergence control signals thereto from said first and second circuits.

2. In a television receiver including a cathode ray image reproducingtube having means for developing a plurality of cathode ray beams andscanning means including a line sweep system for deflecting the beams ata selected line frequency and a field sweep system for deflecting thebeams at a selected field frequency, a control circuit for dynamicallycontrolling the convergence of the cathode ray beams including incombination, convergence coil means adapted to be disposed adjacent thecathode ray tube to develop a field for converging a beam, a firstcircuit connected to and energized by the line and field sweep systemsand including first means for developing convergence control signals atfield frequency series coupled with an adjustable resonant circuit fordeveloping convergence control signals at the line frequency, a secondcircuit connected to and energized by the line and field sweep systemsand including second means for developing further convergence controlsignals at field frequency series connected with an adjustable resonantcircuit for developing convergence control signals at substantially thesecond harmonic of the line frequency, and means coupling saidconvergence coil means to said first and second circuits to applyconvergence control signals thereto from said first and second circuits.

3. In a television receiver including a cathode ray image reproducingtube having means for developing a plurality of cathode ray beams andscanning means including a line sweep system for deflecting the beams ata selected line frequency, a control circuit for dynamically controllingthe convergence of the cathode ray beams including in combination,convergence coil means disposed adjacent the cathode ray tube to developa field for converging a beam, a first series tuned circuit connected tothe line sweep system for developing convergence control signals at theline frequency, a second series tuned circuit connected to the linesweep system for developing convergence control signals at substantiallythe second harmonic of the line frequency, and means coupling saidconvergence coil means between said first and second circuits to applyconvergence control signals thereto from said first and second circuits.

4. In a television receiver including a cathode ray image reproducingtube having means for developing three cathode ray beams and scanningmeans including a line sweep system for deflecting the beams at aselected line frequency, a control circuit for dynamically controllingthe convergence of the cathode ray beams including in combination,first, second and third convergence coil means each adapted to bedisposed adjacent the cathode ray tube to develop respective fields forconverging the beams, first and second series tuned circuits eachconnected to the line sweep system for developing convergence controlsignals at the line frequency, third and fourth series tuned circuitseach connected to the line sweep system for developing convergencecontrol signals atsubst-antially the second harmonic of the linefrequency, means coupling said first convergence coil means to saidfirst and third tuned circuits to apply convergence control signalsthereto, and means intercoupling said second and third convergence coilmeans and connecting the same to said second and fourth tuned circuitsto apply convergence control signals thereto.

5. In a television receiver including a cathode ray image reproducingtube having means for developing a plurality of cathode ray beams andscanning means including a line sweep system for deflecting the beams ata selected line frequency and a field sweep system for deflecting thebeams at a selected field frequency, the control circuit for dynamicallycontrolling the convergence of the cathode ray beams including incombination, a first source of convergence control signals at the fieldfrequency, a first series resonant network including first inductormeans coupled to said first source of convergence control signals andfirst capacitor means coupled to the line sweep system so that saidfirst series resonant network forms signals of substantially sinusoidalform at the line frequency, a second source of convergence controlsignals at the field frequency, a second series resonant network havingsecond inductor means coupled to said second source of convergencecontrol signals and second capacitor means coupled to the line sweepsystem so that said second series resonant network forms signals ofsubstantially sinusoidal form at the second harmonic of the linefrequency, said first and second sources each comprising a return pathfor signals of line frequency and said first and second inductor meansproviding a path for signals of field frequency, and convergence coilmeans adapted to be disposed adjacent the cathode ray tube, said coilmeans being coupled to said first capacitor means and said firstinductor means and to said second capacitor means and said secondinductor means, so that said first and second sources supply convergencecontrol signals to said convergence coil means through said first andsecond inductor means and said signals of substantially sinus oidal formare applied to said convergence coil means by said first and secondresonant networks.

6. In a television receiver including a cathode ray image reproducingtube having means for developing three cathode ray beams and scanningmeans including a line sweep system for deflecting the beams at aselected line frequency, and a field sweep system for deflecting thebeams at a selected field frequency, a control circuit for dynamicallycontrolling the convergence of the cathode ray beams including incombination, first,

second and third convergence coil means each disposed adjacent thecathode ray tube to develop respective fields for converging the beams,first, second, third and fourth circuit means coupled to the field sweepsystem for developing convergence control signals at the fieldfrequency, first and second series tuned circuits coupled respectivelyto said first and second circuit means and to the line sweep system fordeveloping convergence control signals at the line frequency, third andfourth series tuned circuits coupled respectively to said third andfourth circuit means and to the line sweep system for developingconvergence control signals at substantially the second harmonic of theline frequency, means coupling said first convergence coil means betweensaid first and third tuned circuits to apply thereto convergance controlsignals at line and field frequencies, variable impedance means couplingsaid second and third convergence coil means in parallel and meanscoupling said parallel connected second and third convergence coil meansbetween said second and fourth tuned circuits to apply theretoconvergence control signals at line and field frequency with saidvariable impedance means providing a signal balancer between said secondand third convergence coil means.

7. In a television receiver including a cathode my image reproducingtube having means for developing three cathode ray beams and scanningmeans including a line sweep system for deflecting the beams at aselected line frequency, and a field sweep system for deflecting thebeams at a selected field frequency, a control circuit for dynamicallycontrolling the convergence of the cathode ray beams including incombination, first, second and third inductor means each adapted to bedisposed adjacent the cathode ray tube to deveolp respective fields forconverging the beams, first and second circuits each coupled to the linesweep system for developing convergence control signals at the linefrequency, third and fourth circuits each coupled to the field sweepsystem for developing convergence signals at the field frequency, meanscoupling said first inductor means between said first and third circuitsto apply convergence control signals thereto, and variable meanscoupling said second and third inductor means together and between saidsecond and fourth circuits to apply convergence control signals thereto.

8. In a television receiver which includes a housing having therein acathode ray image reproducing tube with means for developing a pluralityof cathode ray beam components, and scanning means including a linesweep system for deflecting the beam components at a selected linefrequency and a field sweep system for deflecting the beam components ata selected field frequency, the combination including, field producingmeans adapted to be disposed adjacent the cathode ray tube forconverging the beam components, a control circuit for developingconvergence control signals, said control circuit being constructed as aunit separate and removable from the 1 television receiver housing, afirst plurality of conductors for applying the convergence controlsignals from said control circuit to said field producing means, and asecond plurality of conductors connected to the line sweep system and tothe field sweep system for energizing said control circuit, said controlcircuit including a plurality of variable means for regulating the waveform of convergence control signals developed therein.

9. In a television receiver unit including a cathode ray imagereproducing tube having means for developing a plurality of cathode raybeam components, and scanning means including a line sweep system fordeflecting the beam components at a selected line frequency and a fieldsweep system for deflecting the beam components at a selected fieldfrequency, including in combination, field producing means adapted to bedisposed adjacent the cathode ray tube for converging the beamcomponents, a control circuit for developing convergence controlsignals, said control circuits being constructed on a chassis separateand removable from the television receiver unit,

a first plurality of conductors for applying the conver- 55 gencecontrol signals from said control circuit to said field producing means,and a second plurality of conductors connected to the line sweep systemand to the field sweep system for energizing said control circuit,

said control circuit including variable reactance means,

and a plurality of variable resistors for regulating the wave form ofconvergence control signals developed therein, and said first and secondplurality of conductors being of respective lengths to permitpositioning of said control circuit so that the screen of the cathoderay image reproducing tube may be viewed as said variable reactancemeans and said variable resistors are manually regulated. V

10. In a television receiver which includes a housing having therein acathode ray image'reproducing tube with means for developing a pluralityof cathode ray beam components, and scanning means including a linesweep system for deflecting the beam components at a selected linefrequency and a field sweep system for deflecting the beam components ata selected field frequency, the combination including, field producingmeans adapted to be disposed adjacent the cathode ray tube forconverging the beam components, a control circuit for developingconvergence control signals, said control circuit being constructed as aunit separate and removable from the television receiver housing, afirst plurality of conductors for applying the convergence controlsignals from said control circuit to said field producing means, asecond plurality of conductors connected to the line sweep system and tothe field sweep system for energizing said control circuit'by respectiveline and field signals developed with respect to a reference point, saidcontrol circuit including means providing low impedance to the referencepoint at line frequency for at least one of said first plurality ofconductors and low impedance to the reference point at field frequencyfor another of said first plurality of conductors, and said controlcircuit further including a plurality of variable means for regulatingthe wave form of convergence control signals developed therein.

11. In a television receiver having a cathode ray image reproducing tubehaving means for developing a cathode ray beam component, a line sweepsystem for deflecting the beam component and a field sweep system forfurther deflecting the beam component: a control system for the cathoderay beam components, including in combination, first and second fieldproducing means adapted to be disposed adjacent the cathode ray tube todevelop respective field's for influencing two beam components, firstcircuit means including a capacitor and tunable inductor connected tothe line sweep system to develop first control signals at the linefrequency, second circuit means connected to the field sweep system todevelop second control signals at the field frequency, energizing meansfor energizing one of said sweep systems with an operating directcurrent potential, a variable balancing inductor interconnecting saidfirst and second field producing means and connecting the same to saidfirst circuit means and means coupling said first and second fieldproducing means to said energizing means and said second circuit meansthereby to energize the same with the first and second control signalsand a direct current dependent upon the energization of said one of saidsweep systems.

12. In a television receiver including a cathode ray image reproducingtube having means for developing a plurality of cathode ray beams andscanning means including a line sweep system for deflecting the beams ata selected line frequency and a field sweep system for deflecting thebeams at a selected field frequency, a control circuit for dynamicallycontrolling the convergence of the cathode ray beams including, incombination, a plurality of single winding inductors disposed adjacentthe cathode ray tube to develop respective fields for converging thecathode ray beams, a first adjustable circuit connected to and energizedby the line, and field sweep systems and including first means fordeveloping convergence control signals at field frequency and secondmeans for developing convergence control signals'at the line frequency,a second adjustable circuit connected to and energized by the fieldsweep system and including third means for developing convergencecontrol signals at field frequency, and connecting means coupling saidinductors in parallel 7 between said first and second circuits to applyconvergence control signals thereto.

No references cited.

